Many people lambasted the alleged “mistake” made by the US-led coalition, with some reporting that civilian casualties from the strike had reached 85.

Rights watchdog Amnesty International said in a statement that the US-led coalition must do more to prevent civilian deaths.

“Anyone responsible for violations of international humanitarian law must be brought to justice and victims and their families should receive full reparation,” Amnesty’s interim Middle East director Magdalena Mughrabi said, Reuters reports.

Manbij has been the focus of US military action in previous weeks. Footage shows airstrikes hitting five Isis targets simultaneously earlier this month.

The observatory said at least 104 civilians have died from air strikes since the start of the Manbij offensive in late May.

Syria’s main opposition body, the High Negotiations Committee, criticised both the US-backed Syria Democratic Forces (SDF) and the coalition, which it blamed for what it said were hundreds of civilian deaths around Manbij.

“The lives of Syrian civilians are being lost in their hundreds whilst there is a deafening international silence,” it said in a letter addressed to UN Secretary General Ban Ki-moon.

Colonel Chris Garver, a spokesman for the US coalition against Islamic State in Syria and Iraq, said it was looking into reports of civilian deaths but was being “extraordinarily careful to make sure” air strikes were killing IS fighters.

The UN High Commissioner for Human Rights recently voiced concern for the roughly 70,000 civilians believed to be trapped between warring parties in Manbij.

“Civilians have...reportedly been killed if they leave their homes or attempt to flee.

“Families are unable to access local cemeteries to bury their relatives who have died or been killed, and are burying them in their gardens or keeping the corpses in bunkers,” Zeid Ra’ad Al Hussein said.

“The town has no electricity or water at present, and no medical facilities are known to be operating. As the SDF closes in on the city, (Islamic State) has not permitted civilians to leave the area.”